is High the device is switched on. The diagnostic

circuitry detect the low drop voltage.

In this case the DIAG output is going low and can

mute the power output stage to avoid noise on

the loudspeaker.The two internal switches can

switch the stabilized output voltage with P-MOS

Transistors to one of the outputs 2 and 3 with low

drop. This is useful to switch the AM and FM cir-

cuitry on or off.

Low active. It’s possible to drive the AM/FM switch

The driver for the external High side switch can

switch on and off the external pnp transistor. The

drop detection circuitry avoid the damage of the

external power pnp transistor.

To supply the varicaps and the PLL-opamp of the

car radio a second very low drop 10 V regulator is

available. This regulator in dropout has a typical

resistance of 50

Ω.

Function of the external High side switch

driver

Fig 2 shows the principle circuitry of the external

High side switch. Fig. 3 shows the switch on/off

phase of the external High side switch. At the

time t0 the microcontroller switches on (curve 1 =

output signal of the microcontroller).

The signal on the HSON pin of the L4952 is shown

on curve 2. At t1 the external Power pnp is

comparator compares the drop of the external pnp.

In case of normal operation the drop is smaller than

In case of failure (that mean a higher drop than

(curve 4). If an error is detected it will be stored in

the internal error flip-flop. The external pnp can

only be switched on again after having turned

Figure 4: Logic input currents versus input

voltage

Figure 3: Stand by consumption versus

temperature

Supply voltage rejection (C = 10

µF, ESR = 4.7Ω,

Load at OUT4 = 10k

Ω)

Figure 5: Supply rejection versus Frequency.

OUT2 propagation delay (Load = 100

Ω)

Figure 6: OUT2 propagation delay (Load = 100

Ω)

Typical Characteristics (Note 4)

L4952

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